Add some tests for debug info behavior (#24650)

In particular, the behavior being discussed in #20462
Also decouple settings.DEBUG_LEVEL (which is the final debug
level output) from cases where we just need e.g. intermediate DWARF.
This will hopefully make cases like "full optimizations + source maps"
more clear.

Author: dschuff

test/test_other.py

@@ -3156,6 +3156,7 @@ def test_dwarf_sourcemap_names(self):
       (['-g2', '-gsource-map'], False, True, True),
       (['-gsplit-dwarf', '-gsource-map'], True, True, True),
       (['-gsource-map', '-sERROR_ON_WASM_CHANGES_AFTER_LINK'], False, True, True),
+      (['-Oz', '-gsource-map'], False, True, True),
     ]:
       print(flags, expect_dwarf, expect_sourcemap, expect_names)
       self.emcc(test_file(source_file), flags, js_file)
@@ -9190,21 +9191,24 @@ def test_ctor_ordering(self, args):
   # test debug info and debuggability of JS output
   @crossplatform
   def test_binaryen_debug(self):
-    for args, expect_emit_text, expect_clean_js, expect_whitespace_js, expect_closured in [
-        (['-O0'], False, False, True, False),
-        (['-O0', '-g1'], False, False, True, False),
-        (['-O0', '-g2'], False, False, True, False), # in -g2+, we emit -g to asm2wasm so function names are saved
-        (['-O0', '-g'], True, False, True, False),
-        (['-O0', '--profiling-funcs'], False, False, True, False),
-        (['-O1'],        False, False, True, False),
-        (['-O2'],        False, True,  False, False),
-        (['-O2', '-gz'], False, True,  False, False), # -gz means debug compression, it should not enable debugging
-        (['-O2', '-g1'], False, False, True, False),
-        (['-O2', '-g'],  True,  False, True, False),
-        (['-O2', '--closure=1'],         False, True, False, True),
-        (['-O2', '--closure=1', '-g1'],  False, True, True,  True),
+    for args, expect_clean_js, expect_whitespace_js, expect_closured in [
+        (['-O0'], False, True, False),
+        (['-O0', '-g1'], False, True, False),
+        (['-O0', '-g2'], False, True, False), # in -g2+, we emit -g to asm2wasm so function names are saved
+        (['-O0', '-g'], False, True, False),
+        (['-O0', '--profiling-funcs'], False, True, False),
+        (['-O0', '-gline-tables-only'], False, True, False),
+        (['-O1'], False, True, False),
+        (['-O3'], True, False, False),
+        (['-Oz', '-gsource-map'], False, True, False), # TODO: fix this (#20462)
+        (['-O2'], True,  False, False),
+        (['-O2', '-gz'], True,  False, False), # -gz means debug compression, it should not enable debugging
+        (['-O2', '-g1'], False, True, False),
+        (['-O2', '-g'],  False, True, False),
+        (['-O2', '--closure=1'], True, False, True),
+        (['-O2', '--closure=1', '-g1'], True, True,  True),
       ]:
-      print(args, expect_emit_text, expect_clean_js, expect_whitespace_js, expect_closured)
+      print(args, expect_clean_js, expect_whitespace_js, expect_closured)
       delete_file('a.out.wat')
       cmd = [EMCC, test_file('hello_world.c')] + args
       print(' '.join(cmd))

tools/building.py

@@ -163,9 +163,11 @@ def lld_flags_for_executable(external_symbols):
   # wasm-ld can strip debug info for us. this strips both the Names
   # section and DWARF, so we can only use it when we don't need any of
   # those things.
-  if settings.DEBUG_LEVEL < 2 and (not settings.EMIT_SYMBOL_MAP and
-                                   not settings.EMIT_NAME_SECTION and
-                                   not settings.ASYNCIFY):
+  if   (not settings.GENERATE_DWARF and
+        not settings.EMIT_SYMBOL_MAP and
+        not settings.GENERATE_SOURCE_MAP and
+        not settings.EMIT_NAME_SECTION and
+        not settings.ASYNCIFY):
     cmd.append('--strip-debug')
 
   if settings.LINKABLE:

tools/cmdline.py

@@ -409,6 +409,7 @@ def consume_arg_file():
           settings.EMIT_NAME_SECTION = 1
         # In all cases set the emscripten debug level to 3 so that we do not
         # strip during link (during compile, this does not make a difference).
+        # TODO: possibly decouple some of these flags from the final debug level (#20462)
         settings.DEBUG_LEVEL = 3
     elif check_flag('-profiling') or check_flag('--profiling'):
       settings.DEBUG_LEVEL = max(settings.DEBUG_LEVEL, 2)

tools/link.py

@@ -2411,7 +2411,7 @@ def phase_binaryen(target, options, wasm_target):
       building.handle_final_wasm_symbols(wasm_file=wasm_target, symbols_file=symbols_file, debug_info=intermediate_debug_info)
       save_intermediate_with_wasm('symbolmap', wasm_target)
 
-  if settings.DEBUG_LEVEL >= 3 and settings.SEPARATE_DWARF and generating_wasm:
+  if settings.GENERATE_DWARF and settings.SEPARATE_DWARF and generating_wasm:
     # if the dwarf filename wasn't provided, use the default target + a suffix
     wasm_file_with_dwarf = settings.SEPARATE_DWARF
     if wasm_file_with_dwarf is True: